• Journal of the Institute of Electronics Engineers of Korea SC
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• v.39 no.4
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• pp.25-35
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• 2002

This work describes an 8b 200MHz time-interleaved subranging analog-to-digital converter (ADC) based on a single-poly digital CMOS process. Two fine ADCs for lower digital bits of the proposed ADC employ a time-sharing double-channel architecture to increase system speed and a new reference voltage switching scheme to reduce settling time of the reference voltages and chip area. The proposed intermeshed resistor string, which generates reference voltages for fine ADCs, improves linearity and settling time of the reference voltages simultaneously. The proposed sample- and-hold amplifier(SHA) is based on a highly linear common-drain amplifier and passive differential circuits to minimize power consumption and chip area with 8b accuracy and employs input dynamic common mode feedback circuits for high dynamic performance at a 200MHz sampling rate. A new encoding circuit in a coarse ADC simplifies the signal processing between the coarse ADC and two successive fine ADCs.

• Magazine of the Korea Concrete Institute
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• v.7 no.1
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• pp.117-125
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• 1995

Bond test was carried out to assess the effect of several variables on bond characteristics between reinforcing bar and concrete. Key variables are concrete compressive strength($f_c$'=340, 460, 6513, 904kg/$cm^2$), concrete cover (25, 38, 51, 105, IlOmm), and bar diameter(Dl3 and D22). Confining effect and bar spacing are not taken into account. Thirty-two specimens subjected to uniaxial tension were tested under hypothesis uniform bond stress distribution along the reinforcing bar embeded in concrete. Failure mode was examined and local bond stress versus slip relationship diagrams were represented to show effect of the above variables, also test results(u1timate bond stress) were compared with bond and development provisions of the ACI Building Code(AC1 318-89) and proposed equations from previous research. According to analysis, borld stress and ultimate bond stress increased although compressive strength increased beyond the ACI Building Code upper limit. Therefore in calculating development length. compressive strength effect(exceeding 700kg /$cm^2$) should be accounted.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.91-99
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• 2020

Post-installed anchors were widely used due to its workable benefits. Regarding the resistance performance of anchors, the critical edge distance is presented to minimize the impact of concrete splitting. In the case of actual anchors, however, it is difficult to obtain the ideal edge distance. The purpose of this study is to identify resistance performance and behavior characteristics that contain complex elements such as concrete crack occurring under tensile load. Tensile tests were conducted based on the standard method. Failure shape and the resistance characteristics that do not have the critical edge distance were derived by tensile load. Parametric analysis according to the boundary condition was performed to simulate the actual tensile behavior, through a nonlinear finite element model based on the specimen. Consequently therefore, verifying analysis results the resistance mechanism can be applied through boundary conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.205-212
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• 2006

In recent investigations, reinforced concrete beams strengthened with Carbon Fiber Sheets (CFS) subjected to fatigue loading were reported to be failed at the ends of CFS by its debonding. U-shaped CFS were attached to both ends of the CFS when fatigue tests on strengthened beams were conducted to delay and/or prevent fatigue failures of adhesive interface. The experimental parameters of this study were the usage of anchorage at the ends of CFS, the number of CFS layers, and the applied load levels of 60%~90% of the static ultimate load obtained from the static tests. The failure modes and the load cycle-deflection relations were observed and discussed from the experimental results. Those results also showed that the U-shaped anchoring system changes the fatigue failure modes and influences greatly on the fatigue capacity of the strengthened beams.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.10-16
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• 2015

Recently, RCM(reliability centered maintenance) process is introduced and applied for the planning and implementing efficient and effective maintenance system in terms of optimal rolling stock maintenance. Particularly, cost-time benefits analysis associated with the implementation of RCM for rolling stock maintenance is necessary and required for railway operator in advance. The RCM process was primarily starting from military, airplane and nuclear industries and is now adapted in railway industry for local railway operators. This paper focuses on suggesting the way of connecting the RCM process with railway maintenance activities in the railway operation field. Thus, in order to introduce and establish reliability activities, it needs to review and evaluate the maintenance environment in the organizational point of view. Based on these reviews and evaluations, various maintenance methodologies are reviewed for customizing local railway field situations and establish specific process in the application of major systems on the reliability technology. In this paper, the railway RCM process is proposed for the establishment and construction of the systematic and optimal maintenance system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1154-1162
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• 2016

This paper proposes a fast-transient digital LDO(Low dropout) regulator with binary-weighted current control technique. Conventional digital LDO takes a long time to stabilize the output voltage, because it controls the amount of current step by step, thus ringing problem is generated. Binary-weighted current control technique rapidly stabilizes output voltage by removing the ringing problem. When output voltage reliably reaches the target voltage, It added the FRZ mode(Freeze) to stop the operation of digital LDO. The proposed fast response digital LDO is used with a slow response DC-DC converter in the system which rapidly changes output voltage. The proposed digital controller circuit area was reduced by 56% compared to conventional bidirectional shift register, and the ripple voltage was reduced by 87%. A chip was implemented with a $0.18{\mu}F$ CMOS process. The settling time is $3.1{\mu}F$ and the voltage ripple is 6.2mV when $1{\mu}F$ output capacitor is used.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.321-330
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• 2006

In order to remodel old aged reinforced concrete buildings, it is often required to extend the residence area of the buildings by increasing the slab area. The slab area is usually extended by attaching a new slab to the existing slab with hinged joint or rigid joint. Transmission of the loads of the attached slabs to the existing slabs depends on the connecting methods, such as hinged or rigid connection. In this research, 8 specimens and 24 RC slabs connected by rigid joints were tested. The new slab was connected to the existing slab by three types of rigid joints using dowel bars and longitudinal tensile bars. Main parameters of the slabs were three types of the rigid joints, anchor length of steel bars(0, 50, 60, 100, and 120mm), development length of steel bars(100, 200, and 300mm), and the spacing of the steel bars(150, 200, 300, and 450mm). The test results indicated that the flexural strength of the RC test slabs having various types of rigid joints was approximately the same to that of the slab without any connections.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.69-77
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• 2002

To acquire the dynamic response and design the controller of the airship, the longitudinal motion of the airship with respect to the vertical gust, which is the nonlinear system, was studied. The effects of the apparent mass and moment of the airship delay the dynamic response and the settling time, which are slower than those of conventional airplanes. The current object of the airship is designed to cruise at 500~1000m altitude. At that height, the atmospheric conditions are generally unstable by wind gust. In this paper, it has been studied for the case of vertical gust, since the apparent mass effects are dominant in has been studied for the case of vertical gust, since the apparent mass effects are dominant in that plane. In addition to the study of the dynamic responses of the airship, the controller was designed using the PID-controller. When the gust was applied, airship responses were recovered of equilibrium states. However, it takes too ling time for recovery and the speed of airship is reduced. So, the aim in this paper was to fasten the recovery speed and to get back the cruising velocity. The control parameters were determined from the stability mode analysis, and the control inputs were the thrust and the elevator deflection angle.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.503-514
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• 2011

In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.